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Fuse Tap - Add-A-Circuit & why you should be using them

The "ADD-A-Circuit" fuse tap has become very popular, and rightfully so. There is nothing worse than using a CHEAP little brass fuse tap on one blade of the fuse, because they often lose contact. When they lose contact, your plow controller will shut off. Far too many think they have a problem with their controller, and buy a new one, because the controller keeps shutting off randomly. It is only after that they realize it is not a controller problem. In many cases it is too late, because many places do not allow returns on electrical items (my shop included). The main reason for this rule is that you can fry an electronic device if you wire it incorrectly. The store has no idea if this happened or not, and there are too many dishonest customers out there these days, unfortunately.

THE most important thing when installing one of these Add-A-Circuit Fuse Taps is to make SURE you have it installed properly. Sounds stupid, but if you are not thinking, or you are ignorant, it WILL work no matter how you plug it in (for the original circuit you are tapping), but one way you will have NO PROTECTION at all for the original circuit. This defeats the whole purpose of using it! Installed wrong your accessory will have no power.

As you can see in the above picture, power MUST enter the side that is fused. IF power was to enter the other blade, the accessory would not work, but the original circuit would have no protection, because it would bypass the fuse. How do you determine which side has power in the cavity in the fuse box? Use a test light or a volt meter. With the vehicle fuse boxes getting more and more crowded, and more and more relays, it is sometimes difficult to find a place for it, where it can be installed properly.

Above is a 2011 Toyota Tacoma fuse box. You can see by design, IF power came in on the other blade, it would be impossible to use, because the Add-A-Circuit would not fit. So there are some limitations.

What circuit should you tap for power? Well the bad news is most vehicles do not come with spare circuits anymore, BUT that makes no difference. I say that because you are adding a circuit to the power supply TO the circuit, not adding load to the accessory it is feeding. What I try to tap is an accessory that has a fuse in the fuse box, but does not exist on the vehicle (when possible). For instance, I just installed a plow on a 2014 Ram 3500 pickup. According to Chrysler, the only acceptable place to get power is from the accessory outlet in the cab. They want you to pull the center cluster, and tap the wire feeding the accessory outlet (which I did). However, this fuse box (Chrysler calls it a TIPM (Totally Integrated Power Module) had quite a few circuits that would have been perfect to tap. Such as a sunroof fuse (the truck did not have a sunroof) or the rear accessory outlet (the truck was a standard cab; no rear outlet), I did not look more, but often there is a fuse for heated rear seats, but the truck does not have rear seats, or if it does, they are not heated. GM trucks will often have all the circuits for rear SUV accessories that a pickup does not have, so you can safely tap them. The only rule I suggest is to not tap a 5 amp circuit for an accessory that uses a 10 amp fuse. Try to match ie; if your accessory uses a 10 amp fuse, tap a 10 amp circuit, or a 15 amp circuit, do not tap a 5 amp circuit. I say this because the on board computers (more now than ever) often monitor loads of various circuits, and if the computer sees a high amp draw, it can or will kill power to that circuit.

So what are the benefits to using an Add-A-Circuit Fuse Tap? As I mentioned above, it is secure, and will not wiggle, resulting in your accessory shutting off. Another great benefit is that you know WHERE your accessory fuse IS. Instead of having to crawl around under the dash to have to check for a blown fuse, it is right in the fuse box. The Add-A-Circuit comes in all the "flavors" too, ATC, ATM, ATM Low Profile, and even the latest ATR Micro 2. What this means is that you do not have to keep a different type of fuse on hand just for your accessory. You can buy the same type of Add-A-Circuit that your vehicle uses. You might notice the 2011 Tacoma picture above I used an ATM fuse tap. This was because I had one, and it fit, and I did not know to expect the Toyota to have low profile fuses. Of course since then (immediately actually) I bought a bag of Low Profile ATM fuse taps.

Now I mentioned Chrysler above and how they want you to tap the accessory outlet circuit for power. They also mention that if your accessory needs more than a certain amount of amps to use that power wire to trigger a relay that can then feed the accessory. I have done this multiple times. The nice thing is the relay gets power when the ignition is turned on, which energizes the relay, feeding power to your accessory (or even multiple accessories) or your accessory switch. When it comes to accessories, fuse taps and relays are your friends.